In chapter 8, what does Mr. Wilson say would be sinful?

Chillingworth wants to take a guess as to who the father of Pearl is. Wilson suggests that it would be a sin to accuse the wrong man,

"Nay; it would be sinful, in such a question, to follow the clew of profane philosophy," said Mr. Wilson. "Better to fast and pray upon it; and still better, it may be, to leave the mystery as we find it, unless Providence reveal it of its own accord. Thereby, every good Christian man hath a title to show a father's kindness towards the poor, deserted babe."